The null ritual
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Gerd Gigerenzer, Stefan Krauss and Oliver Vitouch The Sage handbook of quantitative methodology for the social sciences, 2004 John C Maxwell link |
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Giusi Moffa
Bioinformatics group, University of Regensburg
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Gerd Gigerenzer, Stefan Krauss and Oliver Vitouch The Sage handbook of quantitative methodology for the social sciences, 2004 John C Maxwell link |
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The earth is round (p < .05)
Jacob Cohen, 1994, American Psychologist.
"...this naked emperor has been shamelessly running around for a long time."
Statistical Inference: A Commentary for the Social and Behavioural Sciences.
Michael Oakes, 1986, Wiley
Misinterpretations of Significance: A Problem Students Share with Their Teachers?
Heiko Haller and Stefan Krauss
Methods of Psychological Research Online 2002, Vol.7, No.1
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2 suspects: textbooks and statistics teachers psychology departments of 6 German universities |
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What can be concluded from a significant result?
Suppose you have a treatment that you suspect may alter performance on a certain task. You compare the means of your control and experimental groups (say 20 subjects in each sample). Further, suppose you use a simple independent means t-test and your result is (t = 2.7, d.f. = 18, p = 0.01). Please mark each of the statements below as “true” or “false.” False means that the statement does not follow logically from the above premises. Also note that several or none of the statements may be correct.
Haller and Krauss asked 44 students, 39 lecturers and professors of psychology and 30 statistics teachers.
| p_value: the probability of the observed data (or of more extreme data points), given that the null hypothesis $H_0$ is true, defined in symbols as $p(D \vert H_0)$. |
Percentage of participants in each group who endorsed at least one of the 6 statements.
Percentage of false answers in the three groups.